Ser. No. 07/262,201 discloses a method of monitoring the progress of crystallization of a crystalline silicate product e.g. a metallosilicate zeolite, by measuring the specific electrical conductivity of the synthesis mixture. The method was based upon the finding that different silicates exhibited changes in the specific conductivity of the synthesis mixture during the course of crystallization and that, although the character of the changes varied from one material to another, the changes with a single material were peculiar to that material and therefore permitted a correlation to be established between the measured conductivity and the degree of crystallization achieved. Once established, the correlation between conductivity and crystallinity enabled the progress of crystallization to be monitored either in a batch or a continuous crystallizer. The monitored values of conductivity permitted, moreover, the crystallization conditions to be controlled so as to achieve the desired degree of crystallinity. This method of control was of particular utility with continuous crystallization operations because it enabled product of consistent crystallinity to be obtained. The method was simple, rapid and permitted equipment of a robust, reliable character to be used in commercial size equipment.
Reference is made to Ser. No. 07/262,201 for a full description of the method and its use in the production of crystalline silicate products.